Study On Oxidation Mechanism Of Cold Strip Steel In Annealing Furnace And Its Application

With the increasingly serious market situation,the major iron and steel enterprises between the increasingly fierce competition,control product defects,improve product quality is our goal.Cold-rolled and galvanized production line as the main production line of Jingtang's cold-rolled product output,carrying high-end automotive panels and high-end home appliance board production tasks,but with the annealing furnace oxidation of various types of surface defects are still very serious.For example,the selective oxidation of galvanized DP steel,galvanized steel surface will produce a large number of missing plating defects;even the furnace back to the oxygen content is too high will produce the entire surface of DP steel yellow oxide color defects;Of the lye after annealing furnace in the strip after the formation of white spots on the surface and so on.Therefore,in order to solve the above-mentioned problems in the oxidation of the furnace,through the in-depth study of production line DP steel selective oxidation and a variety of color defects produced by the following control measures:(1)Based on the study of selective oxidation mechanism and influencing factors of galvanized DP steel,it is concluded that the surface leakage of galvanized DP steel is due to the selective oxidation of Si and Mn elements,and the method of preoxidation-reduction can solve the problem of galvanized surface of galvanized DP steel.(2)According to the selective oxidation characteristics of P element,the method of improving the hydrogen content in the heated section of the furnace area is effective to improve the surface color difference of the phosphorus-containing high strength steel.(3)In view of the problem of yellowing in the surface of DP steel,through the comparative analysis and exclusion screening,find out the surface of the yellowing is due to the furnace area is caused by elevated oxygen content.By using a high hydrogen in the fast cooling section and oxygen into nitrogen displacement method,effective solution of yellowing of DP steel surface.(4)By controlling the problem of reducing the strip edge and changing the tangential flow of the cold rolled product,it is possible to effectively improve the blue edge of the strip.